The present invention relates to nuclear power plant systems and more particularly to a nozzle penetration device for a nuclear reactor pressure vessel closure head.
Such a nozzle penetration is known from Swiss Pat. No. 38 37 06. The penetration, which consists of an austenitic material, is screwed into the ferritic portion of the closure. This tension coupling is subject to great stress during temperature changes due to the different coefficients of expansion. The groove provided in the region of the joint weld provides no compensation for the stresses on the screw coupling, since the differences in stress are present in this region also. There is no possibility of influencing the stresses with this design, nor for constructing e.g., a desired prestressing in the region of the tension coupling.